The invention of the present application relates to a chiral lead catalyst and to a method of asymmetric aldol reaction. More precisely, the invention of the present application relates to a novel chiral lead catalyst that enables high yield and high optical selectivity and enables asymmetric synthesis in mild conditions, and to a method of using the said catalyst for asymmetric aldol reaction.
The realization of a method for asymmetric synthesis with high yield and good optical selectivity has become an important issue for chemical synthesis in such fields as medicine, fragrance and the like. In asymmetric synthesis, catalyst-assisted methods are especially attracting attention.
As such catalysts, those with chiral ligand compounds coordinated on metal elements have been proposed. However, such conventional chiral catalysts are limited in the type of reaction to which they are applicable, and often require strict reaction conditions such as, completely anhydrous conditions and extremely low temperatures, thereby restricting reaction conditions and operationality.
On the other hand, the inventors of the present application have found that certain metal compounds are stable in or in the presence of water and serve as Lewis acid catalysts, and that by using such compounds, basic and important carbon-carbon bond-forming organic synthesis reactions such as aldol reaction and Diels-Alder reaction proceed smoothly; based on such findings, the inventors have thus proposed novel catalyst systems.
Taking in consideration the above-mentioned inventors"" knowledge and new proposals, the object of the present invention is to solve the problems of conventional asymmetric synthesis, and to provide a novel catalyst which is widely applicable and enables asymmetric synthesis with high yield and high optical selectivity under mild conditions even in the presence of water, and simplifies the reaction operation. Also, the object of the invention is to provide a method of asymmetric aldol reaction using this catalyst, which is basic and important for producing optically active xcex2-hydroxycarbonyl compounds.
In order to solve the above-mentioned problems, the invention of the present application firstly provides a chiral lead catalyst comprising a lead compound of the following formula:
Pb(ORf)2
(wherein Rf represents a fluorine-containing alkylsulfonyl group)
and a chiral crown ether compound having the structure of the following formula: 
The invention of the present application secondly provides the chiral lead catalyst wherein the lead compound is a lead triflate; thirdly, the present invention provides the chiral lead catalyst wherein the binaphthyl ring of the chiral crown ether compound is substituted with hydrocarbon groups or halogen atoms.
Fourthly, the invention of the present application provides a method of asymmetric aldol reaction for the production of a hydroxyketone compound, comprising the reaction of an aldehyde reactant with a silyl enolether compound in the presence of the catalyst of any of the above first to third inventions, in an aqueous solvent. Fifthly, the invention provides the method of asymmetric aldol reaction wherein the aqueous solvent comprises water and alcohol.